Human Clone Produces Stem Cells

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Human Clone Produces Stem Cells

A cloned embryo at the eight-cell stage. View Slideshow *Editor's note: Hwang Woo-suk has admitted to faking his human cloning and stem cell work, and his published data has been retracted from the journal *Science.

Korean researchers have created a human clone and derived the first cloned stem cells from it – a significant advance toward using the cells to replace those damaged by diseases like diabetes and Alzheimer's.

A Korean woman now has a set of cells that could one day replace any damaged or diseased cell in her body with little worry of rejection, if researchers can get stem cells to work therapeutically.

The study, which will be published in the Feb. 13 issue of the journal Science, will be presented Thursday at the annual meeting of the American Association for the Advancement of Science in Seattle.

While researchers have cloned animals like sheep, cats and cows before this study, researchers had been unable to make the jump to monkeys or humans and believed cloning primates posed a unique obstacle. Now, the Korean researchers show they have perfected a cloning technique, also known as somatic cell nuclear transfer, that works in humans and potentially other primates.

"When I saw the first version of this manuscript back in June 2003, it came like any other e-mail you get," said Jose Cibelli, a professor of animal biotechnology at the University of Michigan who co-authored the paper. "They wanted me to comment on the manuscript and recommend where to submit it, and when I saw the data I almost fell off my chair."

The Korean researchers, led by veterinary cloning expert Woo Suk Hwang and gynecologist Shin Yong Moon of Seoul National University in South Korea, not only created a robust clone that divided into hundreds of cells, but also extracted a stem cell "line," or a group of cells that can potentially replicate indefinitely. So far the line has copied itself 70 times.

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Scientists have extracted stem cells from embryos in the past, hoping to one day use them as medicine. But they worried that the patient's body would reject stem cells taken from someone else. So for the past several years, various groups around the world have been trying to first create a clone, which would be a patient's exact biological match, then take stem cells from it.

Researchers have said they believe that some stem cells taken from embryos can be coaxed to become almost any type of cell in the human body, a characteristic known as "pluripotency." The stem cells in the Korean study differentiated into retinal, bone and other types of cells when implanted into mice.

Advanced Cell Technology, a private company in Worcester, Massachusetts, announced in a splashy Wired magazine cover story in January that it had cloned an embryo to the 16-cell stage. But the company apparently didn't extract stem cells from the embryo, and it wasn't clear how long the clone survived.

It's significant that the Korean research went through a stringent peer-review process in order to be published in Science, scientists say. Advanced Cell Technology has published just one study in an online scientific journal on its human-cloning experiments. In that study, the researchers – including Cibelli, who worked there at the time – achieved a clone with only six cells.

The Korean advance also rekindles ethical protests from some religious and anti-abortion groups. Since the embryo is destroyed when stem cells are extracted, they contend the process is murder. A handful of bills to ban cloning have languished in Congress for the past several years. None has passed, however, because therapeutic cloning is often tied to reproductive cloning, which rogue scientists have threatened to use to produce babies – although they offer no scientific proof that they're close to reaching their goal. Most researchers agree legislation should ban reproductive cloning and support therapeutic cloning.

"In this case there was no sperm, no uterus, there was no vision for this to be a human being," said Bernard Siegel, director of the Genetics Policy Institute. "This is entirely something with the potential to create cures, understanding and treatment of medical conditions, and it's a real step in the right direction."

To create a clone, researchers take an egg from a woman and remove the nucleus. They replace it with a cell from the person to be cloned. They then use chemicals or zap it with electricity to kick-start cell division.

The Koreans had 242 eggs to work with, donated from 16 unpaid healthy women who underwent hormone treatment to stimulate their ovaries to produce more eggs than normal.

With so many eggs to work with, the researchers were able to tweak their process to optimize their methodology. First, instead of sucking the nucleus out with a pipette, which in other experiments sometimes damaged proteins that control cell division, the team nicked a small hole in the egg and gently squeezed the nucleus out.

In their fourth and most successful protocol, the researchers got 19 of 66 cloned eggs to develop into blastocysts – the embryonic stage when it becomes possible to derive stem cells.

In the United States, President Bush announced in August 2001 that federally funded researchers would be prohibited from creating new embryonic stem cell lines, and would be allowed to use only the limited number of lines that already had been created. Researchers in the United States believe the mandate has severely limited progress in stem-cell research here.

"At the pace we're going we're never going to get there, because we don't have enough funding," Cibelli said. "The federal government will have to put up more money. These cells definitely have the potential to be treatments for many diseases."

The Korean researchers wrote that they could not rule out the possibility that their eggs might have begun spontaneously dividing and were not true embryos, a phenomenon called parthenogenesis. It's a type of reproduction found in many life forms, including flies, ants and lizards, but it doesn't create an embryo in mammals. It's not clear that stem cells from human parthenotes would be useful in therapies.

But genetic tests indicated the Koreans very likely had true embryos, not parthenotes.

"I have no doubt they have done somatic cell nuclear transfer," Cibelli said.